HPGDS and neurodegenerative disease: H-Pgds is a cytosolic protein responsible for the biosynthesis of PGD2 in immune and inflammatory cells such as mast cells or Th2 cells, and is also expressed in the spleen, thymus, skin and liver [26], in the microglia where H-Pgds-produced PGD2 is responsible for the neuroinflammation associated with brain injury and neurodegenerative diseases [31], as well as in trophoblasts, uterine epithelium and endometrial glands at the implantation site of the human decidua [32].